It is known that diethyl .alpha.-acetyl-.alpha.'-methylsuccinate can be prepared in about 63 percent yield by reacting ethyl acetoacetate with ethyl .alpha.-bromopropionate in the presence of sodium hydroxide, potassium iodide and water. Chem. Abs. 62, 13037c abstracting (Zh. Pukl. Khim, 38(2), pp 436-7 (1965). Also, J. Chem. Soc. (London), 4633-40 (1970) reports that this same diester can be prepared in about 47 percent yield by reacting ethyl acetoacetate with ethyl .alpha.-bromopropionate in the presence of sodium in ethanol. Similar disclosures are found at Chem. Abs. 54, 10852h; Chem. Abs. 49, 1565c of J. Chem. Soc. (London) 3313 (1953); and Chem. Abs. 38, 2332 of J. Ind. Chem. Soc., 20, 173-7 (1943). However, it has been found in the studies which led to this invention that neither the aqueous basic system nor the ethanolic basic systems allowed the above alkylation to occur with the less expensive ethyl 2-chloropropionate in place of the ethyl 2-bromopropionate. I have found that using the 2-chloropropionate ester at moderate temperatures (40.degree.-50.degree. C.), no significant alkylation reaction was seen; under more vigorous (higher) temperature conditions, using these base systems, 2-chloropropionate and acetoacetate ester starting materials were consumed but little diethyl .alpha.-acetyl-.alpha.'-methylsuccinate ester accumulated in the product, evidencing that this valuable succinate ester intermediate is somewhat unstable and is further converted to undesired, useless by-products in those reaction mixtures. Those in process development research need and are seeking improved and more economical processes for preparing these esters and using them in preparing useful products.
For additional background to the use of .alpha.-acetyl-.alpha.-methylsuccinate esters in processes for preparing useful drug acid compounds, see British Pat. No. 1,265,800 and Belgian Pat. No. 820,267.